1. Field
The present disclosure relates generally to power supplies and, more specifically, to controllers for switched-mode power supplies.
2. Related Art
Many electronic devices include a power supply to provide the device with a regulated direct current (dc) power source. One type of power supply that may be used to provide the regulated dc source is a switched-mode power supply, which is popular due to its small size, good output regulation, high efficiency, and safety features. Switched-mode power supplies may be used to convert an alternating current (ac) source or a high-voltage dc source into a regulated dc source having a desired voltage. Based on the specific application, different types of switched-mode power supplies with different control methods and different features may be used.
Typically, a switched-mode power supply includes a switching element coupled to an energy transfer element. Common examples of energy transfer elements include a transformer or coupled inductor, where electrical energy received by an input winding on the input side is stored as magnetic energy that may be converted back to electrical energy at the output side.
Switched-mode power supplies typically include a controller for directing the switching element to be switched between an ON state and an OFF state to control the amount of power transferred through the energy transfer element to achieve output regulation and maintain properties of the output between predefined threshold values. For instance, the controller may be implemented in an integrated circuit (IC) having multiple input and output terminals and configured to receive signals representative of the parameters of the switched-mode power supply, process the sensed signals, and generate control signals to control the switching element to regulate the output of the power supply. For example, the controller may receive a feedback signal representative of the output of the power supply. Based on this signal, the controller may adjust the switching characteristics of the switching element to vary the amount of power transferred to the output of the power supply.
Since the operation of the controller is based at least in part on the feedback signal, it is important that the feedback signal accurately reflects the output voltage. Errors in the feedback signal caused, for example, by a short, or unwanted coupling, between the feedback terminal of the controller and an adjacent terminal may result in improper output regulation, thereby causing the power supply to generate an incorrect or dangerously high output voltage.
Thus, circuitry for detecting unwanted couplings between terminals of a controller is desired.